208 INTRODUCTION TO GENERAL SCIENCE 



possible, all the water of the soil should be forced to pass up 

 through the cultivated plants, carrying with it plant food. 

 Any water which passes out of the soil through other means 

 is a loss. The prevention of unnecessary loss of water is 

 called conservation. 



The capillarity of the soil must be broken up, which can be 

 accomplished by loosening the surface, and leaving what is 

 called a dry mulch. There are some practices which seem to 

 produce the desired result, although they cause loss. If the 

 land is rolled, it becomes wetter, yet this dampness is taken 

 from the lower soil, and when the surface water has evapo- 

 rated, as it will shortly, the land will be much drier than it 

 would have been if left unrolled. There is considerable loss 

 due to the winds, as air in motion is capable of absorbing 

 much more water than still air. Therefore windbreaks, 

 which will lessen the velocity of the wind, will tend to prevent 

 evaporation from the surface of the land. 



The first tillage, in preparing the soil for planting, loosens 

 it, and exposes the under layers to the action of the air, and 

 also brings more plant food to the surface. In order that 

 plants may grow well, the surface of the soil must be rather 

 finely broken and loosened, so that the tender roots may 

 easily get a start. After planting, the soil is cultivated chiefly 

 to conserve the water, or to cause the lower water to rise, 

 and come within reach of the plant roots. We learned that 

 moisture moves through soil by means of capillarity. Loosen- 

 ing the soil beneath the surface increases the "capillarity, and 

 causes the water to rise from the lower levels. On the other 

 hand, tilling the surface of the ground causes the pores to be 

 closed and evaporation is prevented. This surface layer of 

 finely pulverized dry material is called a soil mulch, and the 

 process of its formation is called mulching. A rain will 



